The IL-6 response to Chlamydia from primary reproductive epithelial cells is highly variable and may be involved in differential susceptibility to the immunopathological consequences of chlamydial infection.

Bottom Line:
Chlamydia trachomatis infection results in reproductive damage in some women.PBMC responses to the stress response proteases (CtTsp and CtHtrA) did not significantly vary for the different participant cohorts.We have demonstrated that IL-6 may be a key factor for the chlamydial disease outcome in humans, given that primary human reproductive epithelial cell culture showed considerable variation in IL-6 response to Chlamydia or chlamydial proteins, and that the presence of live Chlamydia (but not UV killed) during co-culture resulted in a reduced IL-6 response suggesting this response may be moderated by the presence of the organism.

Background: Chlamydia trachomatis infection results in reproductive damage in some women. The process and factors involved in this immunopathology are not well understood. This study aimed to investigate the role of primary human cellular responses to chlamydial stress response proteases and chlamydial infection to further identify the immune processes involved in serious disease sequelae.

Results: Laboratory cell cultures and primary human reproductive epithelial cultures produced IL-6 in response to chlamydial stress response proteases (CtHtrA and CtTsp), UV inactivated Chlamydia, and live Chlamydia. The magnitude of the IL-6 response varied considerably (up to 1000 pg ml(-1)) across different primary human reproductive cultures. Thus different levels of IL-6 production by reproductive epithelia may be a determinant in disease outcome. Interestingly, co-culture models with either THP-1 cells or autologous primary human PBMC generally resulted in increased levels of IL-6, except in the case of live Chlamydia where the level of IL-6 was decreased compared to the epithelial cell culture only, suggesting this pathway may be able to be modulated by live Chlamydia. PBMC responses to the stress response proteases (CtTsp and CtHtrA) did not significantly vary for the different participant cohorts. Therefore, these proteases may possess conserved innate PAMPs. MAP kinases appeared to be involved in this IL-6 induction from human cells. Finally, we also demonstrated that IL-6 was induced by these proteins and Chlamydia from mouse primary reproductive cell cultures (BALB/C mice) and mouse laboratory cell models.

Conclusions: We have demonstrated that IL-6 may be a key factor for the chlamydial disease outcome in humans, given that primary human reproductive epithelial cell culture showed considerable variation in IL-6 response to Chlamydia or chlamydial proteins, and that the presence of live Chlamydia (but not UV killed) during co-culture resulted in a reduced IL-6 response suggesting this response may be moderated by the presence of the organism.

Figure 4: Dependence of HeLa IL-6 and IL-1β response on cellular signalling pathways. The secretion of IL-6 into the media from HeLa or HeLa with THP-1 cultures in response to the various stimulants is shown in the graphs. The IL-6 response at 96 hours is shown in Fig A and B. A) HeLa. B) HeLa with THP-1 co-culture. C) HeLa IL-1β response at 24 h and D) HeLa and THP-1 co-culture IL-1β levels at 24 h. (n = 3) Unpaired two-tailed t-tests have been performed between cohorts.

Mentions:
A caspase-1 inhibitor was tested because caspase-1 initially activates IL-1β as part of the inflammasome response (reviewed [28]). Inhibition of caspase-1 actually resulted in increased IL-6 production in response to all stimulants (Figure 4), but in HeLa only cultures there was no effect on the IL-6 secretion except in response to live Chlamydia where the levels also significantly increased (Figure 4). Wedelolactone inhibits IKK, a kinase involved the final stages of NF-κB activation cascade [27]. IKK inhibition did not alter the IL-6 levels secreted into the media under any of the culture conditions (Figure 4). PD98059 is a broad MEK inhibitor which results in decreased downstream JNK, STAT and p38 pathways induction (reviewed, [29]). U0126 inhibits MEK1/2, leading to decreased ERK1/2 signalling. Broad MEK inhibition did decrease the IL-6 secretion in response to CtHtrA, CtTsp, and live Chlamydia in the HeLa only cell culture (Figure 4). In the co-culture model, IL-6 secretion in response to CtHtrA and CtTsp was significantly reduced by broad MEK (PD98089) or MEK1/2 inhibition (U0126) (Figure 4).

The IL-6 response to Chlamydia from primary reproductive epithelial cells is highly variable and may be involved in differential susceptibility to the immunopathological consequences of chlamydial infection.

Figure 4: Dependence of HeLa IL-6 and IL-1β response on cellular signalling pathways. The secretion of IL-6 into the media from HeLa or HeLa with THP-1 cultures in response to the various stimulants is shown in the graphs. The IL-6 response at 96 hours is shown in Fig A and B. A) HeLa. B) HeLa with THP-1 co-culture. C) HeLa IL-1β response at 24 h and D) HeLa and THP-1 co-culture IL-1β levels at 24 h. (n = 3) Unpaired two-tailed t-tests have been performed between cohorts.

Mentions:
A caspase-1 inhibitor was tested because caspase-1 initially activates IL-1β as part of the inflammasome response (reviewed [28]). Inhibition of caspase-1 actually resulted in increased IL-6 production in response to all stimulants (Figure 4), but in HeLa only cultures there was no effect on the IL-6 secretion except in response to live Chlamydia where the levels also significantly increased (Figure 4). Wedelolactone inhibits IKK, a kinase involved the final stages of NF-κB activation cascade [27]. IKK inhibition did not alter the IL-6 levels secreted into the media under any of the culture conditions (Figure 4). PD98059 is a broad MEK inhibitor which results in decreased downstream JNK, STAT and p38 pathways induction (reviewed, [29]). U0126 inhibits MEK1/2, leading to decreased ERK1/2 signalling. Broad MEK inhibition did decrease the IL-6 secretion in response to CtHtrA, CtTsp, and live Chlamydia in the HeLa only cell culture (Figure 4). In the co-culture model, IL-6 secretion in response to CtHtrA and CtTsp was significantly reduced by broad MEK (PD98089) or MEK1/2 inhibition (U0126) (Figure 4).

Bottom Line:
Chlamydia trachomatis infection results in reproductive damage in some women.PBMC responses to the stress response proteases (CtTsp and CtHtrA) did not significantly vary for the different participant cohorts.We have demonstrated that IL-6 may be a key factor for the chlamydial disease outcome in humans, given that primary human reproductive epithelial cell culture showed considerable variation in IL-6 response to Chlamydia or chlamydial proteins, and that the presence of live Chlamydia (but not UV killed) during co-culture resulted in a reduced IL-6 response suggesting this response may be moderated by the presence of the organism.

Background: Chlamydia trachomatis infection results in reproductive damage in some women. The process and factors involved in this immunopathology are not well understood. This study aimed to investigate the role of primary human cellular responses to chlamydial stress response proteases and chlamydial infection to further identify the immune processes involved in serious disease sequelae.

Results: Laboratory cell cultures and primary human reproductive epithelial cultures produced IL-6 in response to chlamydial stress response proteases (CtHtrA and CtTsp), UV inactivated Chlamydia, and live Chlamydia. The magnitude of the IL-6 response varied considerably (up to 1000 pg ml(-1)) across different primary human reproductive cultures. Thus different levels of IL-6 production by reproductive epithelia may be a determinant in disease outcome. Interestingly, co-culture models with either THP-1 cells or autologous primary human PBMC generally resulted in increased levels of IL-6, except in the case of live Chlamydia where the level of IL-6 was decreased compared to the epithelial cell culture only, suggesting this pathway may be able to be modulated by live Chlamydia. PBMC responses to the stress response proteases (CtTsp and CtHtrA) did not significantly vary for the different participant cohorts. Therefore, these proteases may possess conserved innate PAMPs. MAP kinases appeared to be involved in this IL-6 induction from human cells. Finally, we also demonstrated that IL-6 was induced by these proteins and Chlamydia from mouse primary reproductive cell cultures (BALB/C mice) and mouse laboratory cell models.

Conclusions: We have demonstrated that IL-6 may be a key factor for the chlamydial disease outcome in humans, given that primary human reproductive epithelial cell culture showed considerable variation in IL-6 response to Chlamydia or chlamydial proteins, and that the presence of live Chlamydia (but not UV killed) during co-culture resulted in a reduced IL-6 response suggesting this response may be moderated by the presence of the organism.